Last update issued on April 19, 2003 at 03:05 UTC.
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The geomagnetic field was quiet to minor storm on April 18. Solar wind speed ranged between 572 and 699 km/sec under the influence of a high speed stream from coronal hole CH32.
Solar flux measured at 20h UTC on 2.8 GHz was 107.8. The planetary A
index was 20 (STAR Ap - based on the mean of three hour interval ap indices: 20.4).
Three hour interval K indices: 25444333 (planetary), 24444323 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight there were 5 spotted regions on the visible disk. Solar flare activity was moderate. A single M class event was recorded during the day.
Region 10334 decayed slowly and quietly.
Region 10335 decayed and could soon become spotless.
Region 10336 was quiet and stable.
New region 10337 rotated partly into view at the southeast limb. This region has been fairly active over the last couple of days. The corona is hot above the region and further M class flares are possible. Flare: M1.1 (impulsive) at 19:58 UTC. Additionally a long duration C1 event started late in the day in this region and peaked early on April 19.
Spotted regions not yet numbered by SEC/NOAA:
[S140] A new region emerged inside the southern part of coronal hole CH34 (the development of the region began a couple of days ahead of spots becoming visible) on April 18. Penumbra has developed on both polarities. Location at midnight: N07W05
April 16-18: No obviously geoeffective CMEs observed.
Coronal hole history (since late October 2002)
Compare today's report with the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
A large trans equatorial southern hemisphere coronal hole (CH32) was in a geoeffective position on April 11-14. A small coronal hole (CH33) in the southern hemisphere was in a geoeffective position on April 18. A recurrent coronal hole (CH34) in the northern hemisphere was in a geoeffective position on April 18-19. A recurrent coronal hole (CH35) in the southern hemisphere is likely to be in a geoeffective position on April 21-22.
Processed SOHO EIT 284 image at 19:06 UTC on April 18. Any black areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to active on April 19-20 while high speed coronal hole streams will cause unsettled to active conditions on April 21-22. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is likely to remain very poor until at least April 23. Propagation along north-south paths is fair and is expected to remain fair until at least April 22. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay.]
|Coronal holes (1)||Coronal mass ejections (2)||M and X class flares (3)|
1) Effects from a coronal hole could reach Earth within the next 5 days.
2) Material from a CME is likely to impact Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.
Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.
Compare to the previous day's image.
Data for all numbered solar regions according to the Solar Region Summary provided by SEC/NOAA. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SEC or where SEC has observed no spots.
|Solar region||Date numbered||SEC
|Location at midnight||Area||Classification||Comment|
classification was AXX
at midnight, area 0010
classification was DKO
|Total spot count:||11||13|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2002.10||167.0||97.5||(91.0 predicted, -3.6)|
|2002.11||168.7||95.0||(85.7 predicted, -5.3)|
|2002.12||157.2||81.6||(81.3 predicted, -4.4)|
|2003.01||144.0||79.5||(78.3 predicted, -3.0)|
|2003.02||124.5||46.2||(73.3 predicted, -5.0)|
|2003.03||131.4||61.5||(67.6 predicted, -5.7)|
|2003.04||118.9 (1)||50.6 (2)||(62.7 predicted, -4.9)|
1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (SEC/NOAA) sunspot number. The official international sunspot number is typically 25-45% less.
This report has been prepared by Jan Alvestad. It is based partly on my own observations and interpretations, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.